Research Publications/Outputs

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Combined atomistic molecular calculations and experimental investigations for the architecture, screening, optimization, and characterization of pyrazinamide containing oral film formulations for tuberculosis management
(2015-12) Adeleke, Oluwatoyin A; Monama, Nkwe O; Tsai, PC; Sithole, Happy M; Michniak-Kohn, BB
To date, effective treatment, prophylaxis, and control of tuberculosis (TB) infection is mainly dependent on the use of drugs. However, patient noncompliance with prescribed anti-TB treatment schemes remains a major problem confronting successful pharmacotherapeutic outcomes. Thus, the development of alternative delivery systems that can improve adherence for the existing anti-TB bioactives has been intensified in recent times. The aim of this investigation was to engineer an optimal, thermodynamically stable oral film (OF) formulation containing a key anti-TB agent, pyrazinamide (PYZ), employing molecular modeling and experimental tools. Four PYZ-loaded film variants (OF 1, OF 2, OF 3, OF 4) were constructed in silico and then prepared in vitro using the Accelrys Materials Studio software and solvent casting method, respectively. Screening and selection of the optimal OF was based on the computation of the total interaction energy (ET), kinetic energy (EK), solubility parameter (S), and cohesive energy density (CED) as well as determining mass, thickness, dissolution and disintegration times, dissolution pH, drug loading capacity, and surface morphology in vitro. OF 2 was selected as the optimal formulation as it displayed the lowest ET (−8006.28 kcal/mol), dissolution time (9.96 min), disintegration time (56.49 s), and weight (39.33 mg); moderate EK (1052.98 kcal/mol); highest S (44.55 (J/cm3)0.5) and CED (1.99 × 109 J/m3), slim dimension (166 μm), good and unvarying drug loading capacity (98.04%), acceptable dissolution pH (6.70), and well-layered surface topography. The drug release behavior of the optimal OF 2 was best elucidated with the zero order (R2 = 0.97) and Korsmeyer–Peppas (R2 = 0.99) models. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC) analyses showed that OF 2 was made of physically mixed multiple component polymeric and nonpolymeric compounds. OF 2 was semicrystalline in nature and displayed a dual phased ex vivo mucosal permeation pattern. In silico and in vitro physicomechanical quantities revealed OF 2’s flexibility, robustness, and compressibility. OF 2 was most stable under controlled environmental humidity, pressure, and temperature conditions in silico and in vitro. OF 2 was potentially non-cytotoxic and biocompatible. Succinctly, this work demonstrated the applicability of a combination of atomistic molecular mechanics and dynamics calculations as well as experimental analyses to the fabrication, screening, optimization, and characterization of drug formulations. Lastly, the fabricated OF 2 formulation can function as a potential alternative for the effective loading and delivery of PYZ.
Deferred slanted-edge analysis: A unified approach to Spatial Frequency Response measurement on distorted images and Colour Filter Array subsets
(2018-03) Van den Bergh, Frans
The slanted-edge method of spatial frequency response (SFR) measurement is usually applied to grayscale images under the assumption that any distortion of the expected straight edge is negligible. By decoupling the edge orientation and position estimation step from the edge spread function construction step, it is shown in this paper that the slanted-edge method can be extended to allow it to be applied to images suffering from significant geometric distortion, such as produced by equiangular fisheye lenses. This same decoupling also allows the slanted-edge method to be applied directly to Bayer-mosaicked images so that the SFR of the color filter array subsets can be measured directly without the unwanted influence of demosaicking artifacts. Numerical simulation results are presented to demonstrate the efficacy of the proposed deferred slanted-edge method in relation to existing methods.
Given a SDN topology, how many controllers are needed and where should they go?
(2018-11) Mamushiane, Lusani; Mwangama, J; Lysko, Albert A
Software Defined Networking (SDN) presents a paradigm shift in network management and configuration. The idea of having an externalized control plane opens many unanswered questions regarding scalability, fault tolerance and performance of the controller. An important question that must be answered is, given a network topology, how many controllers are needed and where should they be placed to satisfy user-specific requirements and constraints. Such requirements range from latency constraints, failure tolerance and fair load distribution. These metrics compete with each other, thus no single best placement is available. In this paper, we focus on controller placement to minimize propagation latency (of control traffic) and CapEx associated with installing a new controller. We apply Silhouette Analysis and Gap statistics to compute the optimal number of controllers to use for a given topology. To determine the optimal locations to place the controllers, we use Partition Around Medoids (PAM) clustering algorithm. We evaluate our solution using the Internet2 topology and then expand our scope to over 10 publicly available WAN topologies. As expected, the answers to controller placement are topology-dependent. However, an evaluation of our algorithms on the Internet 2 topology, recommends two controllers as the optimal number of controllers to use. Surprisingly, our results indicate that one controller suffices to meet latency requirements (though certainly not reliability requirements). Finally, the techniques presented in this work can be extended to tackle other similar placement problems, such as baseband unit placement for 5G cloud radio access network (C-RAN) deployment and fog node placement which appears in the context of edge computing.
Guest editorial: Technology enhanced contextual game-based language learning
(2018-07) Lan, YJ; Botha, Adèle
This special issue aims to provide a platform where researchers can present their research efforts offering insights into: (1) the approaches governing the application of technology to enhance L2 game-based learning in context; (2) the evaluation of game-based language learning in different contexts, such as the real world, conventional classroom and the virtual world, with technological support; (3) the comparison of gamebased learning outcomes obtained through the use of different technologies in conventional L2 classroom contexts and; (4) the impact of technology enhanced contextual game-based language learning on the transference of knowledge between formal L2 learning and real life application. The process remains open to further research and exploration and the publication of this special issue can facilitate additional understanding as to the potential of contextual games in TELL. After a rigorous review process, ten significant, noteworthy research papers were accepted for inclusion in this special issue. These papers clearly explain how a technologyrich contextual game can be adopted in TELL, thus providing learners, educators and researchers with valuable insights into this domain, from different perspectives.
Multi-threaded compression of Earth observation time-series data
(2017-03) Swanepoel, Derick; Van den Bergh, Frans
Earth observation data are typically compressed using general-purpose single-threaded compression algorithms that operate at a fraction of the bandwidth of modern storage and processing systems. We present evidence that recently developed multi-threaded compression codecs offer substantial benefits over widely used single-threaded codecs in terms of compression efficiency when applied to a selection of moderate resolution imaging spectroradiometer (MODIS) datasets stored in the HDF5 format. Compression codecs from the LZ77 and Rice families are shown to vary in efficacy when applied to different MODIS data products, highlighting the need for compression strategies to be tailored to different classes of data. We also introduce LPC-Rice, a new multi-threaded codec, that performs particularly well when applied to time-series data.
Using information visualisation to give voice to a historical community
(2016-11) Engelbrecht, L; Botha, M; Botha, A
During the Anglo-Boer War a community of women, children and some men were detained in the Mafeking concentration camp. A number of women described their war experiences some years after. The reliability of these testimonies have however been questioned by various authors. Their written testimonies are known as the Huyser collection. The study presents an Information Visualisation solution to visually represent the coherence of facts within the testimonies. The coherence theory states that the truth value of a proposition consists in its coherence within a set of propositions. By visually representing the coherence of the facts in the testimonies, the possible truth value of the facts is highlighted, thereby giving voice to an historical community of former concentration camp inmates. In order to find a solution to the research problem, a design science research approach was followed. The Huyser collection is regarded as Indigenous Knowledge.

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